B40 wet plug

[malj]

Hi, just to continue the saga of my b40 engine running problem, I thought there may be a problem with the electronic ignition on my B40, the engine seemed to be running very lean/ hot and backfiring through the exhaust and sometimes even 8 stroking, anyway I've borrowed a electrix electronic ignition from a mate installed and fitted as per instructions, the bike again ticked over but would not rev and ran very hot, I advanced the ignition as far as the slots on the stator would allow and the bike now runs a lot better but still not right ( I maybe need to pull and refit the rota so as I can advance the ignition a bit more) anyway when I've checked the spark plug it's very wet with un-burnt fuel, anyone had a similar issue or ideas to fix it.

[AdrianS]

Have you checked the carburettor properly and cleaned all the fine drillings within the body? Have you got the recommended jets fitted and the correct ( or approx. correct) adjustment - start with 1 1/4 turn out with the mixture screw?

If so, I would be tempted to refit the standard points and condenser back. Start with a known simple system. Timing only needs to be approx. for these low stressed engines to run. I would take out the plug and adjust the timing so the points are opening perhaps 3/16 inch before TDC and try and start the bike. It should run at these settings and if so make any fine tuning adjustments from there.
Then report back.

[JulianS]

Check assembly of the carb.

The original monoblocs, which take a thick O ring do not have a fibre washer between float seat and carb body. If one is fitted the fuel level is too high and can cause flooding.

The "new" monblocs, which take a thin O ring like the concentric, have a fibre washer between float seat and carb body. The body has a recess machined to seat the fibre washer, see photos of the "new" monobloc. Leave it out and fue level is too low.